New format returned by getSoftwareVersion

[dparker18]

It looks like the new firmware changes the software version string too:

Traceback (most recent call last):
  File "./DPtest.py", line 8, in <module>
    print('SW info:', a.camera.software_information)
  File "/root/python-amcrest/src/amcrest/system.py", line 70, in software_information
    version, build_date = ret.content.decode('utf-8').split()
ValueError: need more than 1 value to unpack

If I print ret.content it's now:
ret.content: b'version=2.420.AC00.17.R,build:2017-03-22\r\n'

I'll add a check for this and PR, thanks for your work!